1. Field of the Invention
The present invention relates generally to satellite communication systems, and is more particularly related to an antenna utilizing feedhorns to transmit and receive signals.
2. Discussion of the Background
Reflector antennas are typically deployed to receive and transmit signals to a communication satellite. Two key components of the reflector antenna are the feed system and the reflector. Depending on the mode of operation (i.e., receiving or transmitting), the feed system either illuminates the reflector, which in turn, collimates the radiation from the feed system to provide an antenna beam, or receives concentrated signals from the reflector. Given the wide deployment of satellite communication systems, it is increasingly important to implement a multiple-beam antenna to exchange signals with multiple satellites using a single antenna.
To simultaneously receive and/or transmit signals to multiple satellites, numerous feedhorns or xe2x80x9cfeedsxe2x80x9d are utilized. The number of satellites that an antenna can simultaneously communicate with depends largely on the number of feedhorns that can physically be mounted on the antenna. Thus, the size of the feedhorns plays an important role in designing a multiple beam antenna.
Another consideration in the design of the multiple beam antenna concerns the capability of the antenna to perform 2-way communication with closely spaced satellites. Current Federal Communications Commission (FCC) regulations allow a minimum spacing of 2xc2x0 between satellites.
One conventional approach employs a dielectric loaded low-noise block converter with feed (LNBF) into the antenna to simultaneously receive signals from different satellites. A drawback with this approach is that the LNBF feed only supports simultaneous reception, not transmission; thus, application of this antenna is limited. Another drawback is that this antenna design is limited to a minimum satellite spacing of about 4xc2x0.
Another traditional antenna uses a corrugated feedhorn with twin waveguide openings (known as a xe2x80x9cSiamese feedxe2x80x9d). As with the above LNBF antenna, this antenna can only receive simultaneously from multiple satellites. Because of the relatively poor performance of this feed, this antenna is not suitable for transmit purposes, as it cannot meet the antenna transmit performance standards set by the FCC (or other regulatory authorities outside the United States). Therefore, this type of feed currently is utilized for receive operation only, as the FCC and other authorities do not presently promulgate mandatory receive antenna performance standards.
Based on the foregoing, there is a clear need for improved approaches for providing multiple beam antennas that can transmit and receive to different satellites, simultaneously.
There is also a need to increase the number of beams that are supported by a single antenna.
There is also a need to enhance performance of the antenna to provide full-duplex communicate with satellites that are spaced less than or equal to 2xc2x0.
Based on the need to increase antenna efficiency and minimize cost, an approach for providing a single antenna that simultaneously transmits and receives to multiple satellites is highly desirable.
According to one aspect of the invention, an antenna apparatus for receiving and transmitting electromagnetic signals from a plurality of closely spaced satellites comprises a feedhorn that is configured to generate a radiation pattern. A dielectric insert is coupled to the feedhorn to alter the radiation pattern of the feedhorn according to the dielectric constant of the dielectric insert. A reflector is configured to produce an antenna beam based upon the altered radiation pattern of the feedhorn. The above arrangement advantageously provides enhanced performance of the antenna system by increasing the number of simultaneous beams per antenna.
According to another aspect of the invention, a method is provided for receiving and transmitting electromagnetic signals from a plurality of closely spaced satellites via a single antenna. The method includes generating a radiation pattern using a feedhorn of the antenna, wherein the feedhorn is coupled to the dielectric insert that alters the radiation pattern of the feedhorn according to a dielectric constant of the dielectric insert. The method also includes producing an antenna beam based upon the generated radiation pattern via a reflector of the antenna. Under this approach, system cost is reduced because the need to use multiple antennas for communicating with different satellites is eliminated.
According to another aspect of the invention, a multiple-beam antenna system for receiving and transmitting electromagnetic signals from a plurality of closely spaced satellites comprises a plurality of feedhorns having respective radiation patterns. Each of the feedhorns has an aperture and a body. A plurality of dielectric inserts are selectively coupled to the plurality of feedhorns to alter the radiation patterns according to dielectric constants of the dielectric inserts. A reflector is configured to produce multiple antenna beams based upon the altered radiation patterns of the feedhorns. The above arrangement advantageously enhances efficiency of the satellite terminals.
In yet another aspect of the invention, an antenna apparatus for receiving and transmitting electromagnetic signals from a plurality of closely spaced satellites comprises a feedhorn that is configured to generate a radiation pattern. A dielectric insert is coupled to the feedhorn to reduce an effective feed aperture size according to a dielectric constant of the dielectric insert. A reflector is configured to produce an antenna beam. This approach reduces the effective aperture size, thereby permitting physically closed spaced feeds, which in turn can generate antenna beams as close as 2xc2x0.